The process of the present invention is particularly applicable, but not necessarily restricted, to the production of sound insulating panels incorporating a preselected contoured and embossed configuration for use in the passenger compartments of automobile vehicles and the like. Composite sound insulating panels of the foregoing type are adapted to be disposed in overlying shape-conforming relationship against structural panels of vehicle bodies, providing for a significant reduction in the transmission of engine and road noise into the passenger compartment, over which a decorative trim panel or carpeting is applied. Typically, such sound insulating panels are applied over the floor pan, the toe board, the dash panel, the rear quarter panels, the trunk, under the hood and over the wheel housings of automobile bodies and must be accurately contoured and embossed to facilitate attachment to the supporting structural panel, such as by fasteners or adhesives, and to provide proper clearance for assembly of ancillary decorative panels and operating components.
Composite contoured sound insulating panels to which the present process is directed comprise a fibrous pad having a dense filled resinous coating applied substantially uniformly on at least one face surface thereof. Typical of the prior art processes heretofore employed in manufacturing such composite panels are those disclosed in U.S. Pat. Nos. 3,429,728 and 3,536,557. In accordance with the foregoing patented processes, fibrous panels are molded to impart a preselected shape-sustaining contour thereto, after which they are die-cut and subsequently are coated with a dense sound insulating substance, such as a highly filled asphaltic or bituminous base material. Considerable difficulty has been encountered in such prior art processes in achieving a uniform coating of the sound insulating material on the molded fibrous pad due to a puddling effect and a shading effect along substantially vertical and angular surfaces. The shading effect necessitates the use of excess coating material to assure attainment of minimum coating weights along such shaded areas.
The application of such hot melt or other high density coating materials has also occasioned some distortion of the molded fibrous pad, causing difficulties during installation and assembly operations of such composite sound insulating panels in vehicle bodies. The surface texture of the sound insulating coating applied in accordance with prior art practices also is somewhat irregular and has occasioned, at times, difficulty of achieving appropriate alignment and registration of the composite contoured panel and the structural components of vehicle bodies.
The present invention overcomes many of the problems and disadvantages associated with prior art practices by providing a process which provides for a more uniform coating of the dense sound insulating layer, achieving thereby improved performance and a conservation of raw material, which enables the application of a desired surface texture or finish to the dense insulating coating, and which provides for a more accurate contouring and embossment of the panel and improved definition of surface contours and embossed areas therein.